by Bob Latino on Mon Dec 20, 2010 2:27 pm
Below are the voltage readings for the ST-120 amp kit
GZ34 or solid state rectifier
Pin 4 to ground – 400 - 425 volts AC
Pin 6 to ground – 400 - 425 volts AC
Pin 2 to ground – 490 – 530 volts DC *
Pin 8 to ground – 490 – 530 volts DC *
Any 6550/KT88
Pin 1 to ground – approx .550 volts DC (depends on bias setting)
Across pins 2 and 7 – 6.0 – 6.5 volts AC
Pin 3 to ground – 470 - 520 volts DC *
Pin 4 to ground – 470 - 520 volts DC *
Pin 5 to ground – minus 50 to minus 62 volts DC
Pin 6 to ground – minus 50 to minus 62 volts DC
Pin 8 to ground – approx .550 volts DC (depends on bias setting)
Quad cap
Section # 1 (SQUARE symbol) ---------- 480 – 530 volts DC *
Section # 2 (HALF CIRCLE symbol) ----- 470 – 525 volts DC *
Section # 3 (NO symbol or CIRCLE) ---- 470 – 525 volts DC *
Section # 4 (TRANGLE symbol) --------- 400 – 440 volts DC *
Central 12AT7 – Pin 1 or pin 6 to ground > 130 – 175 volts DC *
Two outer 12AT7’s – Pin 1 or pin 6 to ground > 255 – 295 volts DC *
Any 12AT7 – across the two incoming heater wires > 6.0 - 6.5 volts AC
“-50 VAC” on driver board > 48 – 58 volts AC
“B+” on driver board > 400 – 440 volts DC *
* means that the voltage readings will be near the top end of the scale if you use a solid state rectifier
Bob
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